Field of the Invention
The present invention relates to a hydraulic drive system.
Background Information
Work machines such as a hydraulic excavator or a wheel loader are equipped with working implement driven by a hydraulic cylinder. Hydraulic fluid discharged from a hydraulic pump is supplied to the hydraulic cylinder. The inside of the cylinder tube is partitioned by a cylinder rod into a first chamber and a second chamber. The cylinder rod expands due to hydraulic fluid being supplied to the first chamber and hydraulic fluid being exhausted from the second chamber. The cylinder rod contracts due to hydraulic fluid being supplied to the second chamber and hydraulic fluid being exhausted from the first chamber.
The hydraulic fluid is supplied via a hydraulic circuit to the hydraulic cylinder. For example, Japan Patent Laid-open Patent Publication JP-A-2009-511831 describes a work machine equipped with a hydraulic closed circuit for supplying hydraulic fluid to the hydraulic cylinder. Potential energy of the working implement is regenerated due to the hydraulic circuit being a closed circuit. As a result, fuel consumption of a motor for driving the hydraulic pump can be reduced.